Reversible drive for microtome feed screw



Jan. 27, 1970 G. mus 3,

REVERSIBLE DRIVE FOR MICROTOME FEED SCREW Filed May 31, 1967 5 Sheets-Sheet 1 Fig.1.

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Jan. 27, 1970 G. IDLIS 3,491,638

REVERSIBLE DRIVE FQR MICROTOME FEED spmaw Filed May 51, 1967 I 5 Sheets-Sheet 2 Jan. 27, 1970 G. IDLIS REVERSIBLE DRIVE FOR MICROTOME FEED SCREW Filed May 31, 1967 5 Sheets-Sheet 3 l I L95 ll l I Jan. 27, 1970 G. nous 3,491,638

REVERSIBLE DRIVE FOR MI CROTOME FEED SCREW Filed May 31, 1967 5 ShetsSheet 4 Jan. 21, 1970 Glows 3,491,638

REVERSIBLE DRIVE FOR MICROTOME FEED SCREW Fi led May 51, 1967 5 Sheets-Sheet 5 .6. F E1939. I

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United States Patent 3,491,638 REVERSIBLE DRIVE FOR MICROTOME FEED SCREW George Idlis, Milton, Mass, assignor to International Equipment Co., Needham Heights, Mass., a corporation of Massachusetts Filed May 31, 1967, Ser. No. 642,004

Int. Cl. B26d 7/06 US. Cl. 83-171 12 Claims ABSTRACT OF THE DISCLOSURE Microtomes are capable of accurately slicing specimens as they are provided with an adjustable pawl and ratchet drive for the feed screw by which the specimen holder is advanced accurately by small increments relative to the blade holder. As the sections are thin, two microns, for example, initial adjustments by means of the pawl and ratchet drive are slow.

The ratchet wheel is accessible at the rear of a microtome so that, with the pawl disengaged at least when the specimen holder is to be retracted, it can be manually turned to enable the specimen holder to be advanced or retracted more rapidly. Such manual adjustments have the disadvantage that, when the microtome is mounted in a cryostat, it is necessary to reach downwardly into the refrigerated chamber and in back of the microtome which is so mounted that the ratchet wheel is faced in a downward direction.

The principal objective of the invention is to provide a reversible drive for the feed screw together with means to disengage the pawl from the ratchet at least during the retraction of the specimen holder.

Another important objective of the invention is to provide a cryostat with the reversible drive of its microtome and its pawl-disengaging means controlled externally of the cryostat.

Yet another objective of the invention is to provide a reversible drive and pawl-disengaging means that are adapted to be made available as an attachment that may be mounted as required 'by space limitations imposed by the cryostat.

In the accompanying drawings, there are shown illustrative embodiments of the invention from which these and other of its objectives, novel features, and advantages will be apparent.

In the drawings:

FIGURE 1 is a partly broken away side view of a cryostat,

' FIGURE 2 is a front view of the microtome,

FIGURE 3 is a partly broken away side view thereof, FIGURE 4 is a like rear view of the microtome, FIGURE 5 is a partly broken away side view of the control box mounted in one position,

FIGURE 6 is a like view with the control box mounted in another position,

FIGURE 7 is a schematic view of the circuitry, and

FIGURE 8 is a side view of a mounting plate for use when the motor is to be positioned at one side of the microtome.

In FIGURE 1, a cryostat, generally indicated at 10, is shown as having an upwardly opening, refrigerated chamber 11 in which is mounted a microtome, generally indicated at 12. The chamber is closed as by a hinged cover 13 having a transversely hinged forward section 14.

While the microtome 12 may be of a different construction, it is detailed in FIGURES 2, 3, and 4 to an extent to enable the invention and its operation to be fully appreciated.

The microtome 12 has a base 15 provided at one side with a vertical guide 16 slidably supporting a slide block 17 for vertical movement. The slide block 17 has parallel ways 18 and 19 extending forwardly and rearwardly thereof. The upper way 18 slidably retains a slide 20 in the front end of which a holder for a specimen S is detachably held by screw clamp 21, one type of holder being indicated at 22.

At the other side of the base 15, there are a pair of supports 23 and 24 for a shaft 25 to the outer end of which there is fixed a hand wheel 26 having a handle 27. As shown in FIGURE 1, the shaft 25 is shown as extending through the side wall of the cryostat 10 with the hand wheel 26 externally thereof. On the other end of the shaft 25, there is a crank 28 having a pivotal connection 29 with a block 30 slidable in the lower way 19 so that, as the shaft 25 is turned, the block 17 moves vertically relative to the base 15.

Adjacent the front of the base 15, there is a bracket 31 slidable forwardly and rearwardly along a way 32 in the base 15 into a desired position in which it is releasably held as by a threaded clamp indicated at 33 in FIGURE 2 and including an actuating lever 34. The bracket 31 has a pair of laterally spaced seats 35, each having an adjusting screw 36 threaded forwardly therethrough. Clamping fingers 37, one for each seat 35, are attached to the brackets 31 by pivots 38. The lower end of each finger has a clamping screw 39 threaded therethrough thereby to enable each finger to clamp a blade 40 against the seats 35 at an angle determined by the seat screws 36.

The blade 40 is below and forwardly of the specimen holder 22 and in order that the specimen S may be sliced, as the block 17 and its holder 22 are moved vertically, it is necessary to provide indexing means for moving the block 17 forwardly as the shaft 25 is turned.

To that end, an end plate 41 is secured to the rear end of the slide block 17 to close the rear end of the way 18. The plate 41 rotatably supports a lead screw 42 on the rear end of which is fixed a ratchet wheel 43. The feed screw 42 extends freely into the chamber 20A in the slide block 20 and is threaded through a nut 44 fixed therein by screws 45 so that, as the ratchet wheel 43 is turned in one direction or the other, the holder 22 is advanced or retracted relative to the blade 40.

In order that the holder 22 may be accurately advanced small increments, two microns, for example, as the shaft 25 is turned, a pawl 46 is mounted on an arm 47 supported by the end plate 41 for rotation independently thereof and yiedlably urged by a spring 49 into operative engagement with the ratchet wheel 43. Adjacent the lever 47, there is a post 50 rotatably supporting an index head 51 having its bottom edge formed to provide an annular series of axially extending steps 52. By way of example, there are eight such steps and each step provides a two micron advance in the position of the vertical path of the specimens relative to the blade 40. The selected step 52 is engaged by a pin 53 extending laterally from the arm 47 thus to limit the arcuate travel of the arm 47 and the open ative movement of the pawl 46.

It will be appreciated that, in practice, not only must the holder 22 be positioned to bring its specimen S into a position to engage the blade, but also the specimen must be trimmed until a section of suitable area can be cut. While the slide 20 may be advanced by turning the hand wheel 26, the practice has been, to enable such adjustments to be made more quickly, for the operator to reach into the cryostat chamber 11 and manually turn the ratchet wheel 43 in the required direction to the desired extent, holding the pawl 46 disengaged when the slide 20 is being retracted.

In accordance with the invention, these adjustments may be made quickly and accurately without the necessity of reaching into the cryostat chamber 11 and behind the microtome 12 This objective is attained, in the embodiment of the invention illustrated by the drawings, by attaching a bracket 54 to the end plate 41. The bracket 54 supports a reversible motor 55 within a housing 56 and having a beveled pinion 57 mounted on its shaft 58 and meshing with a beveled gear 59 coaxial with and attached to the ratchet wheel 43 The bracket 54 has a depending flange 60 on which is mounted a solenoid 61 of the type having a rotor driven cam 62 adapted to turn, say 45, in a predetermined direction from its normal position each time it is energized The cam 62 is disposed so that when it turns, it engages the pawl 46 and turns it out of its operative position in which it holds the ratchet wheel 43 against turning.

-It will thus be appreciated that when the solenoid 61 is energized, and the circuit to the motor 55 is closed, the slide 20 is quickly and easily advanced or retracted by the operator.

A suitable circuit, schematically shown in FIGURE 7 has parallel advance and retract switches 63 and 64 in control of motor leads 65 and 66 and a lead 67. The lead 67 has a rectifier 68, the solenoid 61 and a resistor 69. The solenoid 61 is thus in service if either of the switches 63, 64 is closed.

The lead 65 includes parallel switches 63A and 64A, the switch 63A being operated with the switch 63 and the switch 64A being operated with the switch 64. The switches 63A and 64A have normal positions as shown and in their other positions, they are connected to parallel ground leads 70 and 71, respectively, thereby to effect appropriate control of the direction in which the motor 55 rotates.

In some instances, it may be desired to have the switches mounted on the cryostat 10 and in others, it may be desired to have the microtome controlled more remotely. For that reason, the control box is detailed in FIGURES and 6 and, as generally indicated at 72, has proved satisfactory.

The control box 72, see FIGURES 5 and 6, includes a base 73 of U-shaped section having detachable legs 74 and adapted to be supported by and attached to a vertical or a horizontal surface. Certain of the components of the circuitry are attached to the base 73. A cover 75 includes an end wall 76 provided with an inturned flange 77 attached to the base 73 and a'short flange 78 at its other end provided with forwardly projecting tabs 79. The cover 75, when attached, terminates short of one end of the base 73 and the box is completed by a switch mount, generally indicated at 80 and having walls 80A and 8GB of the same dimensions and disposed at right angles to each other with each formed with an inturned flange 81 having holes 82 for the tabs 79 or for assembly screws 83. The switches are mounted on the wall 80A of the mount and, when the control box is to be attached to a vertical surface, see FIGURE 6, the side wall of the cryostat 10, for example, the button is positioned with its wall 80A, the upper end wall of the control box. When the control box 70 is to be used in a horizontal position, see FIG- URE 5, the mount 80 is positioned with its wall 80B the corresponding end wall.

While, in the cryostat shown in the drawings, there is space to the rear and above the microtome for the motor 55, in other cryostats, the available motor space may be at the rear and at one side of the microtome. For that reason the bracket shown in FIGURE 8 is provided and as it is generally similar to the bracket 54, its corresponding parts are indicated by the suflix addition A to the appropriate reference numerals. The bracket 54A includes a vertically disposed, right angular plate 84 for the support of the motor 55.

From the foregoing, it will be appreciated that a microtome in accordance with the invention is well adapted to provide increased convenience to its users in that it enables the specimen holders to be quickly advanced and retracted into a desired position to start the slicing of the specimens and this is done without the necessity of entering the chamber 11 and without otherwise altering the normal use of the microtome.

I claim:

1. In a microtome, a blade support, a specimen holder, means to move said holder vertically relative to the blade support and to move said holder towards the blade support a predetermined distance each time said support is moved into and out of a predetermined operative position relative to said blade support, said means including a feed screw and a pawl and ratchet to turn said screw in a holderadvancing direction, a screw drive including a motor and operable to efIect retracting movement of said holder, and means operable to disengage said pawl from said ratchet, at least during the retraction of said holder.

2. The microtome of claim 1 in which the motor is reversible.

3. The microtome of claim 2 and a gear connection between the motor and the feed screw.

4. The microtome of claim 1 in which the pawl disengaging means is operated automatically when the drive is operated in a holder-retracting direction.

5. The microtome of claim 1 in which the pawl disengaging means is operated whenever the drive is operated by said motor.

6. The microtome of claim 1 in which the pawl disengaging means includes a solenoid and a member engaging the pawl when the solenoid is operated.

7. The microtome of claim 6 in which the solenoid is of the turning type and the pawl-engaging member is a cam.

8. In combination, a cryostat having a chamber and a microtome in said chamber and including a blade support, a specimen holder, means to move said holder vertically relative to the blade support and to move said holder towards the blade support a predetermined distance each time said support is moved into and out of a predetermined operative position relative to said blade support, said means including a feed screw and a pawl and ratchet to turn said screw in a holder advancing direction, and a screw drive including a motor operable to etfect retracting movement of said holder and means operable to disengage said pawl from said ratchet, and control means for said screw drive mounted on said cryostat externally of the chamber.

9. The combination of claim 8 in which the control includes a box provided with a mount attached to the box in first or second positions, and switches carried by the mount, in the first position of the mount, the switches are exposed at the end of the box and, in the second position thereof, the switches are exposed on the cover of the box.

5 6 10. The combination of claim 9 in which the box inengaging means is electrically operated and is energized cludes a base of U-shaped cross section open at its ends, whenever the motor is in service.

a cover includes a wall at one end secured to said base and a flange at its other end provided with forwardly References C'ted disposed projections, and the mount includes a pair of 5 UNITED STATES PATENTS walls of the same size and shape, each wall including an 2 155 523 4/1939 B h et 1, g3 915 5 X end flange having apertures to receive said projections, 3,077,806 2/1963 l-Iellstrom 83-9155 X the switches being mounted on one of said mount walls. 3,204,424 9/1965 McCormick et al. 83-107 X 11. The combination of claim 8 in which the motor is reversible and the control means includes directional con- 10 JAMES MEISTER Pnmary Exammer trols. US. Cl. X.R.

12. The combination of claim 8 in which the pawl dis- 83-412, 915.5 

